Compressor pulsation dampener



Jufiy 29, 1969 F. .1. GLEASON, JR. ET 3,453,121

COMPRESSOR PULSATION DAMPENER Filed Aug. 25, 1967 M mm wpwm mm m W1 United States Patent 3,458,121 COMPRESSOR PULSATION DAMPENER Frank J. Gleason, Jr., and Russell E. Comstock, Sidney, Ohio, assignors to Copeland Refrigeration Corporation, Sidney, Ohio, a corporation of Michigan Filed Aug. 25, 1967, Ser. No. 663,361 Int. Cl. F04c 29/10, 1/02; F04b 35/04 US. Cl. 230232 4 Claims ABSTRACT OF THE DISCLOSURE Background of the invention In refrigeration systems of the types which have .a small reciprocating hermetic compressor unit and a relatively large charge of refrigerant, and which operate intermittently as in applications such as air conditioning window units, household refrigerators and the like, the piston or pistons of the compressor may be partially or entirely submerged in the liquid in the sump during startup periods, due to the fact that the refrigerant migrates to the crankcase and has an affinity for the oil, substantially increasing the liquid content in the sump during off periods. The underside of the piston acts in effect as a hydraulic pump .and on each stroke drives a column of liquid away from the cylinder against the shell. In most instances, the case is of welded sheet steel construction, the unit is spring suspended, and the speed of the compressor is relatively high. The impulses caused by the jets of liquid thus directed against the side of the casing and by the oscillations of the liquid create objectionable noise and may, due to undesired conditions of synchronism, result in objectionable vibration.

The object of the present invention is to provide a i Description of the invention In the drawing:

FIGURE 1 is a substantially diametric vertical sectional view of a typical refrigeration motor-compressor unit equipped with our invention, and

FIGURE 2 is a cross section taken substantially on the line IIII of FIGURE 1 and looking in the direction of the arrows.

Referring now to the drawing, reference character designates generally the welded casing or shell of a hermetic motor compressor unit of a well known character which is commonly used in refrigeration applications, and which includes therein an electric motor generally designated 12, direct-coupled to .and which drives a single cylinder reciprocating compressor generally designated 14. The structural features of the motor and compressor will not require detailed consideration, being well known in the art. The unitary motor compressor assembly is resiliently supported in the welded sheet steel shell 10 by suitable means including the spring 15, and the shell is in turn supported on resilient supports such as the cushioned feet .16.

Reference character 20 designates a typical level to which the liquid contents (oil .and dissolved refrigerant) may rise during inoperative periods. During operation, the level normally drops to a level near the lowest part of the piston, whereafter the objectionable phenomenon referred to ceases.

We have found that the objectionable vibration and pulsating noises created during starting periods are often caused, in compressors of this general character, by the oscillations of the liquid caused by the underside of the piston, and by the surges of liquid driven against the interior of the shell, as indicated above, and also by the fact that the weight of the total mass represented by the entire unit with its liquid content, and therefore also the natural instantaneous periodicity of such total mass, varies while the refrigerant is escaping from the oil, and 'at certain times the induced oscillations tend to synchronize with the natural frequencies of oscillation of various resilient components, such as those of elements 15 and 16, the coiled outlet tube 22, and the natural periods of vibration of other elements such as sheet metal structure in the environment, some of which components may not even be actual parts of the functioning refrigeration system.

In order to dissipate the transverse movements of the liquid and prevent the pulses of liquid from striking the shell, we provide a baffle structure generally designated 25 in the sump. The baffie is formed of sheet metal and in the construction shown in which the crankcase wall portions 24 extend part way around the throw area, the bafile extends horizontally across the open bottom portion 26 of the crankcase, to which it may be suitably secured as by rivets 28. In a vertical direction the baffle extends downwardly to the bottom of the opening and upwardly to a position above the liquid level 20, but is not sealed at the top or at the bottom, permitting access of oil to the space within the crankcase. The baffle is preferably so shaped that a substantial proportion of its surface is at an angle both to the direction of propagation and the wave front emanating from the back of the piston, such as the crenelated form indicated at 30. Liquid driven against the baffle by inward movement of the piston 32 is thereby redirected in various directions. Further, due to its inclined contours, the baffle tends to reduce audible effects of the pulsations, because the oscillation of the liquid creates successive wave fronts, and different portions of each wave front strike the baflle at different times. It will be noted that this is in contrast to the normal situation in which the shell 10 is substantially smooth and concentric, so that not only does each pulse or surge of liquid strike the shell itself, but to the extent that the surges are of the nature of waves, substantially all of each wave front tends to impact the shell at about the same time with a resultant concentrated shock effect.

As also will be understood, the refrigerant return line 33 opens into the interior of the shell so that intimate contact between the oil and the refrigerant cannot be avoided and under certain conditions the aforementioned excessively high liquid level is likewise unavoidable.

The disclosed construction in actual tests has been found to reduce very largely the shuddering, vibration and excessive noise of the unit during startup.

What is claimed is:

1. In an enclosed compressor construction of the type comprising a housing having an oil sump for maintaining a level of oil in the lower portion thereof and into which a refrigerant inlet opens, a reciprocating pistontype compressor in the housing having a cylinder in the lower part of the housing, the inner end of the cylinder being in liquid-conductive direct flow communication with the sump below the oil level in the latter, and a baffledefining portion blocking an area projected rectilinearly axially of the piston from the piston to the housing and having an open edge portion below said level around which oil may flow, while movement of oil in a straight line from the piston to the housing is prevented.

2. A compressor construction as defined in claim 1 including crankcase portions partially enclosing the compressor and spaced from the housing and carrying said bathe-defining portion.

3. A compressor construction as defined in claim 1 wherein a substantial proportion of said bathe-defining portion lies at an oblique angle to the path of piston movement.

4. A compressor construction as defined in claim 2 wherein a substantial proportion of the baffle-defining portion lies at an oblique angle to the path of piston movement and an opening is provided past a lower 5/1940 Doeg 23058 3/1941 Philipp 230-206 10 ROBERT M. WALKER, Primary Examiner US. Cl. X.R. 2305 8, 206 

